Research

Most environmental processes occur at the interface between different phases of matter present in natural systems. Hence, it is crucial to study the chemistry at the interface of materials in these systems at the molecular level and under environmentally-representative conditions. My research in environmental surface chemistry tackles important and unresolved scientific problems in geochemistry and atmospheric chemistry. We utilize state-of-the-art equipment and computational software to study processes at the gas/solid and liquid/solid interfaces. Below is detailed description of the ongoing research programs in my lab at Laurier:

1- Projects in Atmospheric Chemistry:The
lower atmosphere, known as the troposphere, comprises a large
concentration of minute airborne particles known as aerosols.
Aerosols in the troposphere have complex chemical composition and they
impact our lives in a number of ways. Reduced visibility seen on
hazy days and respiratory health problems are just two examples of
aerosols impact on a regional scale. On a global scale, aerosols
contribute to climate change as they influence the amount of sunlight
reaching the Earth’s surface, alter properties of clouds, and provide
media for chemical reactions in the atmosphere. Computer
simulations of the climate give us the capability of quantifying the
magnitude of aerosols contribution to climate change. Yet aerosols
representation in these simulations is still inadequate mainly because
aerosols are complicated in nature and their reactivity and properties
change with time while suspended in air. Thus, it is imperative
to address scientific questions related to aerosols through
experimental studies to better our understanding of the aerosols impact
on our climate system.

Organic matter on aerosols originates from
pollution stemming from human activity, natural sources (emissions from
trees and animals), and biomass burning. Since reactions occur mainly
on aerosols surfaces, and in order to simplify the complex chemical
nature of aerosols, we prepare and characterize model surfaces composed
of the most abundant chemical compounds identified in real aerosol
particles. We also study the processing and aging of aerosols
caused mainly by reactions with pollutant gases found in the
atmosphere. We use experimental techniques that allow monitoring
reactions on surfaces under controlled environments such as Fourier
transform infrared spectroscopy. Results obtained from these
studies will increase our understanding of the aging process of
aerosols and their overall impact on the global climate.

2- Projects in Interfacial Geochemistry:
Arsenic and its compounds are listed on the pollutant priority
lists of the Canadian Environmental Protection Act (CEPA) and the U.S.
EPA. These compounds are stable in geochemical environments and
identified to pose adverse health effects to humans, including cancer.
The current Canadian interim maximum acceptable limit of total arsenic
in drinking water is 25 micrograms per liter (parts per billion), while
that of the U.S. EPA is 10 ppb.

Arsenic in the environment exists in
two forms: inorganic and organic. Contamination of water bodies
(rivers, steams, groundwater) with inorganic arsenic originates from
the weathering of arsenic-containing ores and minerals and results in
releasing arsenic into water. Other sources also include tailings of
abandoned and recent gold mining operations, and wood preservative
facilities. Inorganic arsenic compounds are known for their high
toxicity, and water contamination with this form of arsenic is
widespread in different parts around the world and in north America
including Canada’s east coast and northwestern territories. In
addition, the organic form of arsenic is found in the environment as a
result of microbial activity and also introduced to the environment
through their historical use as herbicides and through the disposal and land
application of contaminated poultry litter as some organic arsenic
compounds are used as feed additives in the poultry industry.

Our
work in this area is motivated by the fact that potential transformation
of organic arsenic to inorganic arsenic in water and soil pose an
environmental risk. However, the fate of organic arsenic in soils
and natural waters depends to a large extend on how these compounds
interact with soil particles and organic matter derived from the
decomposition of plants. These interactions also affect the rate
at which organic arsenic gets transported from one location to another,
and the rate at which these compounds become available to plants and
other organisms. Our work aims at quantifying the strength
of interactions between organic arsenic compounds with model soil
components using infrared spectroscopy. I am currently collaborating with Professor Ian Hamilton in the Chemistry Department at Laurier in running computational chemistry projects on systems related to our ongoing research program in geochemistry. Specifically, surface complexes of organoarsenical compounds are modeled using theoretical methods to gain further insight into their geometries and to aid in the interpretation of the experimental infrared spectra of interfacial species. Relative Gibbs free energies for ligand exchange reactions at the water/solid interface will also be calculated.

The results we are
looking to obtain from our studies will be used to feed
pollutant-transport models used predict how far can a pollutant plume
travel in the water supply and how long would it take to reach water
distribution facilities. The outcome of these transport models
would be used to help municipalities decide on the implementation of
pollutants-removal technologies from contaminated waters.